JPA EclipseLink实体未刷新

问题描述

当从JPA会话外部更改数据库中的值时，实体没有刷新的问题。例如，我有一个用户实体：

I have a problem with entities not being refreshed when values in the database are changed from outside the JPA session. For instance, I have a user entity:

@Entity
@Cacheable(false)
public class UserBean implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    @OneToMany(mappedBy = "receiver")
    @JoinTable(name = "NOTIFICATIONS_RECEIVED")
    private List<NotificationBean> notificationsReceived;
    ...

}

通知实体：

@Entity
@Cacheable(false)
public class NotificationBean implements Serializable{

    @Id
    @GeneratedValue
    private Long id;

    @ManyToOne
    private UserBean receiver;
    ...

}

我在a JSF应用程序，并具有一个SessionScoped bean，该bean在登录后加载用户并进行存储：

I use this inside a JSF application and have a SessionScoped bean, which loads the user after login and stores it:

@Named("sessionManager")
@SessionScoped
public class SessionManagerBean implements Serializable {

    @PersistenceUnit(unitName = "PU")
    private EntityManagerFactory emf;

    private UserBean user;

    public UserBean getUser() throws Exception {
        if (user == null) {
            FacesContext context = FacesContext.getCurrentInstance();
            HttpServletRequest request = (HttpServletRequest) context.getExternalContext().getRequest();
            String username = request.getRemoteUser();
            if (username != null) {
                EntityManager em = null;
                try {
                    utx.begin();
                    em = emf.createEntityManager();
                    Query query = em.createQuery("SELECT u from UserBean u WHERE u.username = ?1");
                    query.setParameter(1, username);
                    user = (UserBean) query.getSingleResult();
                }
                catch (Exception e) {
                    try {
                        utx.rollback();
                    } catch (Exception e) {
                    } finally {
                    utx.commit();
                    em.close();
                    }
                }
                return user;
            }
        }
    }

    public void refreshUser() {
         EnitytManager em = emf.createEntityManager();
         // similar code as above to retrieve the user from the database
         em.refresh(user);
    }
}

显示通知呼叫的页面 refreshUser（）加载时：

The page which displays the notifications calls refreshUser() when it loads:

<f:metadata>
   <f:event type="preRenderView" listener="#{sessionManager.refreshUser()}" />
</f:metadata>

虽然我的数据没有刷新，但刷新时页面上显示的通知没有更新

The user data is not refreshed though and notifications which are displayed on the page are not updated when I refresh the page.

但是，如果我将 refreshUser（）更改为：

However, if I change refreshUser() to:

public void refreshUser() {
EntityManager em = emf.createEntityManager();
        List<NotificationBean> notifications = em.createNativeQuery("SELECT * FROM NOTIFICATIONBEAN WHERE RECEIVER_ID = " +
               user.getId() + ";").getResultList();
        user.setMatchChallengesReceived(notifications);
}

通知已更新。

我需要从数据库中刷新的通知比我有更多的变量，并且每个通知都需要执行很多代码。我认为 em.refresh（user）应该为我重新加载数据库中所有已更改的变量。我认为这是一个缓存问题，因此我向 UserBean 和 @Cacheable（false） > NotificationBean ，但无效。

I have more variable than notifications that I need to refresh from the database and it would be a lot of code to do the same for each one. I thought em.refresh(user) should reload all variables that have changed from the database for me. I thought it is a caching issue, so I added @Cacheable(false) to UserBean and NotificationBean, but it has no effect.

我在做什么错了？

推荐答案

如果问题出在通知上，则由于未将刷新用户设置为级联刷新，因此很容易。在notificationsReceived映射上设置CascadeType.REFRESH。

If the problem is with notifications, then itis because refreshing user is not set to cascade the refresh. Set the CascadeType.REFRESH on the notificationsReceived mapping.

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